Method for accessing network by user equipment, and access device

ABSTRACT

Embodiments of the present disclosure provide a method for accessing a network by a user equipment (UE), and an access device. The method includes: sending, by a source side access device, an access indication message to a UE, where the access indication message is used to instruct the UE to access a target side access device; or sending, by a source side access device, a first notification message to a target side access device, where the first notification message is used to instruct the target side access device to send, to a UE, access information used to instruct the UE to access the target side access device; and in a process in which the UE accesses the target side access device, maintains a connection between the UE and the source side access device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/917,104, filed on Mar. 9, 2018, which is a continuation of U.S.patent application Ser. No. 14/947,398, filed on Nov. 20, 2015, which isa continuation of International Application No. PCT/CN2013/076113, filedon May 22, 2013. All of the afore-mentioned patent applications arehereby incorporated by reference in their entireties.

TECHNICAL FIELD

Embodiments of the present invention relate to the field ofcommunications technologies, and in particular, to a method foraccessing a network by a piece of user equipment, and an access device.

BACKGROUND

Currently, as intelligent terminals and mobile applications developrapidly, it is getting more difficult for a live network to satisfy anincreasing data volume requirement. With wide deployment of a wirelesslocal area network (WLAN for short below), hotspot covered areasgradually increase; however, during inter-system bearer handover in a3rd generation mobile communications network (3GPP for short below), forexample, a piece of user equipment (User Equipment, UE for short below)is handed over from a 3GPP network to a WLAN, or a UE is handed overfrom a WLAN to a 3GPP network, during the handover, the UE disconnects aconnection between the UE and a source side access device, andre-accesses a target side access device. In the handover process, the UEtransfers all bearers of the source side access device to the targetside access device.

However, in the foregoing handover process, a service interruption iseasily caused, and normal running of a service is affected.

SUMMARY

Embodiments of the present invention provide a method for accessing anetwork by a piece of user equipment, and an access device, so as toresolve a problem that in an inter-system bearer handover process, aservice interruption is easily caused and therefore normal running of aservice is affected.

According to a first aspect, an embodiment of the present inventionprovides a method for accessing a network by a piece of user equipment,including:

-   -   sending, by a source side access device, an access indication        message to a piece of user equipment UE, where the access        indication message is used to instruct the UE to access the        target side access device; or sending, by the source side access        device, a first notification message to a target side access        device, where the first notification message is used to instruct        the target side access device to send, to the UE, access        information used to instruct the UE to access the target side        access device; and    -   in a process in which the UE accesses the target side access        device, maintaining, by the source side access device, a        connection between the UE and the source side access device,        where    -   the connection between the UE and the source side access device        includes a control plane connection between the UE and the        source side access device or a user plane connection between the        UE and the source side access device.

In a first possible implementation manner of the first aspect, beforethe sending, by a source side access device, an access indicationmessage to the UE, the method further includes:

-   -   receiving, by the source side access device, the access        indication message sent by a centralized control node.

With reference to the first aspect or the first possible implementationmanner of the first aspect, in a second possible implementation mannerof the first aspect, the access indication message includes: informationused to indicate an access feature of the target side access device andinformation used to indicate a resource reserved by the target sideaccess device for the UE.

With reference to the method according to any one of the first aspect tothe second possible implementation manner of the first aspect, in athird possible implementation manner of the first aspect, the accessindication message is further used to: after the UE accesses the targetside access device, instruct the UE to maintain the connection betweenthe UE and the source side access device, or disconnect the connectionbetween the UE and the source side access device.

With reference to the method according to any one of the first aspect tothe third possible implementation manner of the first aspect, in afourth possible implementation manner of the first aspect, the methodfurther includes:

-   -   sending, by the source side access device, a first bearer        transfer message to the UE, where the first bearer transfer        message carries a bearer identifier of a bearer between the UE        and the source side access device, and the bearer identifier is        used to instruct the UE to transfer a bearer corresponding to        the bearer identifier to the target side access device.

With reference to the method according to any one of the first aspect tothe third possible implementation manner of the first aspect, in a fifthpossible implementation manner of the first aspect, the method furtherincludes:

-   -   sending, by the source side access device, a bearer identifier        of a bearer between the UE and the source side access device to        the target side access device, where the bearer identifier of        the bearer between the UE and the source side access device is        used to instruct the target side access device to send a second        bearer transfer message to the UE, where the second bearer        transfer message is used to instruct the UE to transfer a bearer        corresponding to the bearer identifier to the target side access        device.

With reference to the method according to any one of the first aspect tothe fifth possible implementation manner of the first aspect, in a sixthpossible implementation manner of the first aspect, the accessindication message is further used to: after the UE accesses the targetside access device, instruct the UE to enter a discontinuous receptionDRX mode.

According to a second aspect, an embodiment of the present inventionprovides a method for accessing a network by a piece of user equipment,including:

-   -   receiving, by a piece of user equipment UE, an access indication        message sent by a source side access device, where the access        indication message is used to instruct the UE to access the        target side access device; or receiving, by the UE, access        information that is sent by the target side access device and        used to instruct the UE to access the target side access device;        and    -   accessing, by the UE, the target side access device according to        the access indication message or the access information, where    -   in a process in which the UE accesses the target side access        device, the UE maintains a connection between the UE and the        source side access device, where the connection between the UE        and the source side access device includes a control plane        connection between the UE and the source side access device or a        user plane connection between the UE and the source side access        device.

In a first possible implementation manner of the second aspect, beforethe receiving, by a piece of user equipment UE, an access indicationmessage sent by a source side access device, the method furtherincludes:

-   -   detecting, by the UE, the target side access device; and    -   reporting, by the UE, a first discovery message to the source        side access device, where the first discovery message is used to        indicate the target side access device detected by the UE.

With reference to the second aspect or the first possible implementationmanner of the second aspect, in a second possible implementation mannerof the second aspect, the access indication message includes:information used to indicate an access feature of the target side accessdevice and information used to indicate a resource reserved by thetarget side access device for the UE.

With reference to the method according to any one of the second aspectto the second possible implementation manner of the second aspect, in athird possible implementation manner of the second aspect, the accessindication message is further used to: after the UE accesses the targetside access device, instruct the UE to maintain the connection betweenthe UE and the source side access device, or disconnect the connectionbetween the UE and the source side access device.

With reference to the third possible implementation manner of the secondaspect, in a fourth possible implementation manner of the second aspect,if the indication information is used to: after the UE accesses thetarget side access device, instruct to disconnect the connection betweenthe UE and the source side access device, after the accessing, by theUE, the target side access device, the method further includes:

-   -   disconnecting, by the UE, the connection between the UE and the        source side access device.

With reference to the method according to any one of the second aspectto the fourth possible implementation manner of the second aspect, in afifth possible implementation manner of the second aspect, the methodfurther includes:

-   -   receiving, by the UE, a first bearer transfer message sent by        the source side access device, where the first bearer transfer        message carries a bearer identifier of a bearer between the UE        and the source side access device, and the bearer identifier is        used to instruct the UE to transfer a bearer corresponding to        the bearer identifier to the target side access device; or        receiving, by the UE, a second bearer transfer message sent by        the target side access device, where the second bearer transfer        message is used to instruct the UE to transfer a bearer        corresponding to a bearer identifier to the target side access        device.

With reference to the method according to any one of the second aspectto the fourth possible implementation manner of the second aspect, in asixth possible implementation manner of the second aspect, the methodfurther includes:

-   -   sending, by the UE, a traffic flow template TFT, a procedure        transaction identifier PTI, and a bearer identifier of a bearer        between the UE and the source side access device to the source        side access device, where the TFT, the PTI, and the bearer        identifier of the bearer between the UE and the source side        access device are used by the source side access device to stop        using a bearer that corresponds to the bearer identifier of the        bearer between the UE and the source side access device to        exchange data with the UE.

With reference to the method according to any one of the second aspectto the sixth possible implementation manner of the second aspect, in aseventh possible implementation manner of the second aspect, the accessindication message is further used to: after the UE accesses the targetside access device, instruct the UE to enter a discontinuous receptionDRX mode, and the method further includes:

-   -   entering, by the UE, the DRX mode according to the access        indication message to exchange data with the source side access        device, or exchange data with the target side access device.

According to a third aspect, an embodiment of the present inventionprovides a method for accessing a network by a piece of user equipment,including:

-   -   sending, by a centralized control node, an access indication        message to a source side access device, so that the source side        access device sends the access indication message to the source        side access device, where the access indication message is used        to instruct the UE to access the target side access device; or    -   sending, by the centralized control node, a second notification        message to a target side access device, where the second        notification message is used to instruct the target side access        device to send, to the UE, access information used to instruct        the UE to access the target side access device.

In a first possible implementation manner of the third aspect, theaccess indication message includes: information used to indicate anaccess feature of the target side access device and information used toindicate a resource reserved by the target side access device for theUE.

With reference to the third aspect or the first possible implementationmanner of the third aspect, in a second possible implementation mannerof the third aspect, the access indication message is further used to:after the UE accesses the target side access device, instruct the UE tomaintain a connection between the UE and the source side access device,or disconnect a connection between the UE and the source side accessdevice.

With reference to the method according to any one of the third aspect tothe second possible implementation manner of the third aspect, in athird possible implementation manner of the third aspect, the accessindication message is further used to: after the UE accesses the targetside access device, instruct the UE to enter a discontinuous receptionDRX mode.

According to a fourth aspect, an embodiment of the present inventionprovides an access device, including:

-   -   a sending module, configured to send an access indication        message to a piece of user equipment UE, where the access        indication message is used to instruct the UE to access the        target side access device; or configured to send a first        notification message to a target side access device, where the        first notification message is used to instruct the target side        access device to send, to the UE, access information used to        instruct the UE to access the target side access device; and    -   a processing module, configured to: in a process in which the UE        accesses the target side access device, maintain a connection        between the UE and the source side access device, where    -   the connection between the UE and the source side access device        includes a control plane connection between the UE and the        source side access device or a user plane connection between the        UE and the source side access device.

In a first possible implementation manner of the fourth aspect, theaccess device further includes:

-   -   a receiving module, configured to: before the sending module        sends the access indication message to the UE, receive the        access indication message sent by a centralized control node.

With reference to the fourth aspect or the first possible implementationmanner of the fourth aspect, in a second possible implementation mannerof the fourth aspect, the access indication message includes:information used to indicate an access feature of the target side accessdevice and information used to indicate a resource reserved by thetarget side access device for the UE.

With reference to the access device according to any one of the fourthaspect to the second possible implementation manner of the fourthaspect, in a third possible implementation manner of the fourth aspect,the access indication message is further used to: after the UE accessesthe target side access device, instruct the UE to maintain theconnection between the UE and the source side access device, ordisconnect the connection between the UE and the source side accessdevice.

With reference to the access device according to any one of the fourthaspect to the third possible implementation manner of the fourth aspect,in a fourth possible implementation manner of the fourth aspect, thesending module is further configured to:

-   -   send a first bearer transfer message to the UE, where the first        bearer transfer message carries a bearer identifier of a bearer        between the UE and the source side access device, and the bearer        identifier is used to instruct the UE to transfer a bearer        corresponding to the bearer identifier to the target side access        device.

With reference to the access device according to any one of the fourthaspect to the third possible implementation manner of the fourth aspect,in a fifth possible implementation manner of the fourth aspect, thesending module is further configured to:

-   -   send a bearer identifier of a bearer between the UE and the        source side access device to the target side access device,        where the bearer identifier of the bearer between the UE and the        source side access device is used to instruct the target side        access device to send a second bearer transfer message to the        UE, where the second bearer transfer message is used to instruct        the UE to transfer a bearer corresponding to the bearer        identifier to the target side access device.

With reference to the access device according to any one of the fourthaspect to the fifth possible implementation manner of the fourth aspect,in a sixth possible implementation manner of the fourth aspect, theaccess indication message is further used to: after the UE accesses thetarget side access device, instruct the UE to enter a discontinuousreception DRX mode.

According to a fifth aspect, an embodiment of the present inventionprovides an access device, including:

-   -   a receiving module, configured to receive an access indication        message sent by a source side access device, where the access        indication message is used to instruct the UE to access the        target side access device; or configured to receive access        information that is sent by the target side access device and        used to instruct the UE to access the target side access device;        and    -   a processing module, configured to access the target side access        device according to the access indication message or the access        information, where    -   in a process in which the UE accesses the target side access        device, the UE maintains a connection between the UE and the        source side access device, where the connection between the UE        and the source side access device includes a control plane        connection between the UE and the source side access device or a        user plane connection between the UE and the source side access        device.

In a first possible implementation manner of the fifth aspect, theprocessing module is further configured to:

-   -   detect the target side access device before the receiving module        receives the access indication message sent by the source side        access device; and    -   the access device further includes:    -   a sending module, configured to report a first discovery message        to the source side access device, where the first discovery        message is used to indicate the target side access device        detected by the UE.

With reference to the fifth aspect or the first possible implementationmanner of the fifth aspect, in a second possible implementation mannerof the fifth aspect, the access indication message includes: informationused to indicate an access feature of the target side access device andinformation used to indicate a resource reserved by the target sideaccess device for the UE.

With reference to the access device according to any one of the fifthaspect to the second possible implementation manner of the fifth aspect,in a third possible implementation manner of the fifth aspect, theaccess indication message is further used to: after the UE accesses thetarget side access device, instruct the UE to maintain the connectionbetween the UE and the source side access device, or disconnect theconnection between the UE and the source side access device.

With reference to the third possible implementation manner of the fifthaspect, in a fourth possible implementation manner of the fifth aspect,if the indication information is used to: after the UE accesses thetarget side access device, instruct to disconnect the connection betweenthe UE and the source side access device, the processing module isfurther configured to:

-   -   after the access module accesses the target side access device,        disconnect the connection between the UE and the source side        access device.

With reference to the access device according to any one of the fifthaspect to the fourth possible implementation manner of the fifth aspect,in a fifth possible implementation manner of the fifth aspect, thereceiving module is further configured to:

-   -   receive a first bearer transfer message sent by the source side        access device, where the first bearer transfer message carries a        bearer identifier of a bearer between the UE and the source side        access device, and the bearer identifier is used to instruct the        UE to transfer a bearer corresponding to the bearer identifier        to the target side access device; or configured to receive a        second bearer transfer message sent by the target side access        device, where the second bearer transfer message is used to        instruct the UE to transfer a bearer corresponding to a bearer        identifier to the target side access device.

With reference to the access device according to any one of the fifthaspect to the fourth possible implementation manner of the fifth aspect,in a sixth possible implementation manner of the fifth aspect, thesending module is further configured to:

-   -   send a traffic flow template TFT, a procedure transaction        identifier PTI, and a bearer identifier of a bearer between the        UE and the source side access device to the source side access        device, where the TFT, the PTI, and the bearer identifier of the        bearer between the UE and the source side access device are used        by the source side access device to stop using a bearer that        corresponds to the bearer identifier of the bearer between the        UE and the source side access device to exchange data with the        UE.

With reference to the access device according to any one of the fifthaspect to the sixth possible implementation manner of the fifth aspect,in a seventh possible implementation manner of the fifth aspect, theaccess indication message is further used to: after the UE accesses thetarget side access device, instruct the UE to enter a discontinuousreception DRX mode, and the processing module is further configured to:

-   -   enter the DRX mode according to the access indication message to        exchange data with the source side access device, or exchange        data with the target side access device.

According to a sixth aspect, an embodiment of the present inventionprovides a centralized control node, including:

-   -   a sending module, configured to send an access indication        message to a source side access device, so that the source side        access device sends the access indication message to the source        side access device, where the access indication message is used        to instruct the UE to access the target side access device; or    -   configured to send a second notification message to a target        side access device, where the second notification message is        used to instruct the target side access device to send, to the        UE, access information used to instruct the UE to access the        target side access device.

In a first possible implementation manner of the sixth aspect, theaccess indication message includes: information used to indicate anaccess feature of the target side access device and information used toindicate a resource reserved by the target side access device for theUE.

With reference to the sixth aspect or the first possible implementationmanner of the sixth aspect, in a second possible implementation mannerof the sixth aspect, the access indication message is further used to:after the UE accesses the target side access device, instruct the UE tomaintain a connection between the UE and the source side access device,or disconnect a connection between the UE and the source side accessdevice.

With reference to the centralized control node according to any one ofthe sixth aspect to the second possible implementation manner of thesixth aspect, in a third possible implementation manner of the sixthaspect, the access indication message is further used to: after the UEaccesses the target side access device, instruct the UE to enter adiscontinuous reception DRX mode.

According to a seventh aspect, an embodiment of the present inventionprovides an access device, including:

-   -   a transmitter, configured to send an access indication message        to a piece of user equipment UE, where the access indication        message is used to instruct the UE to access the target side        access device; or configured to send a first notification        message to a target side access device, where the first        notification message is used to instruct the target side access        device to send, to the UE, access information used to instruct        the UE to access the target side access device; and    -   a processor, configured to: in a process in which the UE        accesses the target side access device, maintain a connection        between the UE and the source side access device, where    -   the connection between the UE and the source side access device        includes a control plane connection between the UE and the        source side access device or a user plane connection between the        UE and the source side access device.

In a first possible implementation manner of the seventh aspect, theaccess device further includes:

-   -   a receiver, configured to: before the sending module sends the        access indication message to the UE, receive the access        indication message sent by a centralized control node.

With reference to the seventh aspect or the first possibleimplementation manner of the seventh aspect, in a second possibleimplementation manner of the seventh aspect, the access indicationmessage includes: information used to indicate an access feature of thetarget side access device and information used to indicate a resourcereserved by the target side access device for the UE.

With reference to the access device according to any one of the seventhaspect to the second possible implementation manner of the seventhaspect, in a third possible implementation manner of the seventh aspect,the access indication message is further used to: after the UE accessesthe target side access device, instruct the UE to maintain theconnection between the UE and the source side access device, ordisconnect the connection between the UE and the source side accessdevice.

With reference to the access device according to any one of the seventhaspect to the third possible implementation manner of the seventhaspect, in a fourth possible implementation manner of the seventhaspect, the transmitter is further configured to:

-   -   send a first bearer transfer message to the UE, where the first        bearer transfer message carries a bearer identifier of a bearer        between the UE and the source side access device, and the bearer        identifier is used to instruct the UE to transfer a bearer        corresponding to the bearer identifier to the target side access        device.

With reference to the access device according to any one of the seventhaspect to the third possible implementation manner of the seventhaspect, in a fifth possible implementation manner of the seventh aspect,the transmitter is further configured to:

-   -   send a bearer identifier of a bearer between the UE and the        source side access device to the target side access device,        where the bearer identifier of the bearer between the UE and the        source side access device is used to instruct the target side        access device to send a second bearer transfer message to the        UE, where the second bearer transfer message is used to instruct        the UE to transfer a bearer corresponding to the bearer        identifier to the target side access device.

With reference to the access device according to any one of the seventhaspect to the fifth possible implementation manner of the seventhaspect, in a sixth possible implementation manner of the seventh aspect,the access indication message is further used to: after the UE accessesthe target side access device, instruct the UE to enter a discontinuousreception DRX mode.

According to an eighth aspect, an embodiment of the present inventionprovides an access device, including:

-   -   a receiver, configured to receive an access indication message        sent by a source side access device, where the access indication        message is used to instruct the UE to access the target side        access device; or configured to receive access information that        is sent by the target side access device and used to instruct        the UE to access the target side access device; and    -   a processor, configured to access the target side access device        according to the access indication message or the access        information, where    -   in a process in which the UE accesses the target side access        device, the UE maintains a connection between the UE and the        source side access device, where the connection between the UE        and the source side access device includes a control plane        connection between the UE and the source side access device or a        user plane connection between the UE and the source side access        device.

In a first possible implementation manner of the eighth aspect, theprocessor is further configured to:

-   -   detect the target side access device before the receiver        receives the access indication message sent by the source side        access device; and    -   the access device further includes:    -   a transmitter, configured to report a first discovery message to        the source side access device, where the first discovery message        is used to indicate the target side access device detected by        the UE.

With reference to the eighth aspect or the first possible implementationmanner of the eighth aspect, in a second possible implementation mannerof the eighth aspect, the access indication message includes:information used to indicate an access feature of the target side accessdevice and information used to indicate a resource reserved by thetarget side access device for the UE.

With reference to the access device according to any one of the eighthaspect to the second possible implementation manner of the eighthaspect, in a third possible implementation manner of the eighth aspect,the access indication message is further used to: after the UE accessesthe target side access device, instruct the UE to maintain theconnection between the UE and the source side access device, ordisconnect the connection between the UE and the source side accessdevice.

With reference to the third possible implementation manner of the eighthaspect, in a fourth possible implementation manner of the eighth aspect,if the indication information is used to: after the UE accesses thetarget side access device, instruct to disconnect the connection betweenthe UE and the source side access device, the processor is furtherconfigured to:

-   -   after the access point accesses the target side access device,        disconnect the connection between the UE and the source side        access device.

With reference to the access device according to any one of the eighthaspect to the fourth possible implementation manner of the eighthaspect, in a fifth possible implementation manner of the eighth aspect,the receiver is further configured to:

-   -   receive a first bearer transfer message sent by the source side        access device, where the first bearer transfer message carries a        bearer identifier of a bearer between the UE and the source side        access device, and the bearer identifier is used to instruct the        UE to transfer a bearer corresponding to the bearer identifier        to the target side access device; or configured to receive a        second bearer transfer message sent by the target side access        device, where the second bearer transfer message is used to        instruct the UE to transfer a bearer corresponding to a bearer        identifier to the target side access device.

With reference to the access device according to any one of the eighthaspect to the fourth possible implementation manner of the eighthaspect, in a sixth possible implementation manner of the eighth aspect,the transmitter is further configured to:

-   -   send a traffic flow template TFT, a procedure transaction        identifier PTI, and a bearer identifier of a bearer between the        UE and the source side access device to the source side access        device, where the TFT, the PTI, and the bearer identifier of the        bearer between the UE and the source side access device are used        by the source side access device to stop using a bearer that        corresponds to the bearer identifier of the bearer between the        UE and the source side access device to exchange data with the        UE.

With reference to the access device according to any one of the eighthaspect to the sixth possible implementation manner of the eighth aspect,in a seventh possible implementation manner of the eighth aspect, theaccess indication message is further used to: after the UE accesses thetarget side access device, instruct the UE to enter a discontinuousreception DRX mode, and the processor is further configured to:

-   -   enter the DRX mode according to the access indication message to        exchange data with the source side access device, or exchange        data with the target side access device.

According to a ninth aspect, an embodiment of the present inventionprovides a centralized control node, including:

-   -   a transmitter, configured to send an access indication message        to a source side access device, so that the source side access        device sends the access indication message to the source side        access device, where the access indication message is used to        instruct the UE to access the target side access device; or    -   configured to send a second notification message to a target        side access device, where the second notification message is        used to instruct the target side access device to send, to the        UE, access information used to instruct the UE to access the        target side access device.

In a first possible implementation manner of the ninth aspect, theaccess indication message includes: information used to indicate anaccess feature of the target side access device and information used toindicate a resource reserved by the target side access device for theUE.

With reference to the ninth aspect or the first possible implementationmanner of the ninth aspect, in a second possible implementation mannerof the ninth aspect, the access indication message is further used to:after the UE accesses the target side access device, instruct the UE tomaintain a connection between the UE and the source side access device,or disconnect a connection between the UE and the source side accessdevice.

With reference to the centralized control node according to any one ofthe ninth aspect to the second possible implementation manner of theninth aspect, in a third possible implementation manner of the ninthaspect, the access indication message is further used to: after the UEaccesses the target side access device, instruct the UE to enter adiscontinuous reception DRX mode.

According to the method for accessing a network by a piece of userequipment, and the access device that are provided in the embodiments ofthe present invention, a source side access device sends an accessindication message to a UE, where the access indication message is usedto instruct the UE to access a target side access device; or a sourceside access device sends a first notification message to a target sideaccess device, where the first notification message is used to instructthe target side access device to send, to a UE, access information usedto instruct the UE to access the target side access device; and in aprocess in which the UE accesses the target side access device, thesource side access device maintains a connection between the UE and thesource side access device. Therefore, in the process in which the UEaccesses the target side access device, the source side access devicemaintains the connection between the UE and the source side accessdevice; therefore, a service interruption is not caused.

BRIEF DESCRIPTION OF THE DRAWINGS

To describe the technical solutions in the embodiments of the presentinvention more clearly, the following briefly introduces theaccompanying drawings required for describing the embodiments.Apparently, the accompanying drawings in the following description showsome embodiments of the present invention, and persons of ordinary skillin the art may still derive other drawings from these accompanyingdrawings without creative efforts.

FIG. 1 is a flowchart of Embodiment 1 of a method for accessing anetwork by a piece of user equipment according to the present invention;

FIG. 2 is a flowchart of Embodiment 2 of a method for accessing anetwork by a piece of user equipment according to the present invention;

FIG. 3 is a flowchart of Embodiment 3 of a method for accessing anetwork by a piece of user equipment according to the present invention;

FIG. 4 is a flowchart of Embodiment 4 of a method for accessing anetwork by a piece of user equipment according to the present invention;

FIG. 5 is a signaling flowchart of Embodiment 1 of a method foraccessing a network by a piece of user equipment according to thepresent invention;

FIG. 6 is a signaling flowchart of Embodiment 2 of a method foraccessing a network by a piece of user equipment according to thepresent invention;

FIG. 7 is a signaling flowchart of Embodiment 3 of a method foraccessing a network by a piece of user equipment according to thepresent invention;

FIG. 8 is a signaling flowchart of Embodiment 4 of a method foraccessing a network by a piece of user equipment according to thepresent invention;

FIG. 9 is a schematic structural diagram of Embodiment 1 of an accessdevice according to the present invention;

FIG. 10 is a schematic structural diagram of Embodiment 2 of an accessdevice according to the present invention;

FIG. 11 is a schematic structural diagram of Embodiment 3 of an accessdevice according to the present invention;

FIG. 12 is a schematic structural diagram of Embodiment 4 of an accessdevice according to the present invention;

FIG. 13 is a schematic structural diagram of Embodiment 5 of an accessdevice according to the present invention;

FIG. 14 is a schematic structural diagram of Embodiment 6 of an accessdevice according to the present invention;

FIG. 15 is a schematic structural diagram of Embodiment 7 of an accessdevice according to the present invention; and

FIG. 16 is a schematic structural diagram of Embodiment 8 of an accessdevice according to the present invention.

DETAILED DESCRIPTION

To make the objectives, technical solutions, and advantages of theembodiments of the present invention clearer, the following clearlydescribes the technical solutions in the embodiments of the presentinvention with reference to the accompanying drawings in the embodimentsof the present invention. Apparently, the described embodiments are apart rather than all of the embodiments of the present invention. Allother embodiments obtained by persons of ordinary skill in the art basedon the embodiments of the present invention without creative effortsshall fall within the protection scope of the present invention.

Technologies described in the embodiments of the present invention maybe applied to various communications systems, for example, current 2Gand 3G communications systems and a next-generation communicationssystem, for example, a Global System for Mobile Communications (GSM), aCode Division Multiple Access (CDMA) system, a Time Division MultipleAccess (TDMA) system, a Wideband Code Division Multiple Access (WCDMA)system, a Frequency Division Multiple Access (FDMA) system, anOrthogonal Frequency-Division Multiple Access (OFDMA) system, asingle-carrier FDMA (SC-FDMA) system, a General Packet Radio Service(GPRS) system, a Long Term Evolution (LTE) system, and othercommunications systems of this type.

A piece of user equipment involved in the embodiments of the presentinvention may be a wireless terminal or a wired terminal. The wirelessterminal may refer to a device that provides a user with voice and/ordata connectivity, a handheld device with a radio connection function,or another processing device connected to a radio modem. The wirelessterminal may communicate with one or more core networks via a radioaccess network (RAN). The wireless terminal may be a mobile terminal,such as a mobile phone (also referred to as a “cellular” phone) and acomputer with a mobile terminal, for example, may be a portable,pocket-sized, handheld, computer built-in, or in-vehicle mobileapparatus, which exchanges voices and/or data with the radio accessnetwork. For example, the wireless terminal may be a device such as apersonal communication service (PCS,) phone, a cordless telephone set, aSession Initiation Protocol (SIP) phone, a wireless local loop (WLL)station, or a personal digital assistant (PDA). The wireless terminalmay also be referred to as a system, a subscriber unit, a subscriberstation, a mobile station, a mobile, a remote station, an access point,a remote terminal, an access terminal, a user terminal, a user agent, auser device, or a piece of user equipment.

Either of a source side access network device and a target side accessdevice involved in the embodiments of the present invention may be adevice, such as a base station or a radio network controller (RNC),independently disposed in a radio access network (RAN), or may be afunctional module in the foregoing devices on a radio access networkside.

A base station (for example, an access point) may refer to a device incommunication with a wireless terminal via one or more sectors on an airinterface in an access network. The base station may be configured tomutually convert a received over-the-air frame and an IP packet andserve as a router between the wireless terminal and a rest portion ofthe access network, where the rest portion of the access network mayinclude an Internet protocol (IP) network. The base station may alsocoordinate attribute management of the air interface. For example, thebase station may be a base station (BTS) in GSM or CDMA, may be a basestation (NodeB) in WCDMA, or may be an evolved NodeB (NodeB, eNB, ore-NodeB,) in LTE, which is not limited in the embodiments of the presentinvention.

A base station controller may be a base station controller (BSC) in GSMor CDMA, or a radio network controller (RNC) in WCDMA, which is notlimited in the embodiments of the present invention.

An access network device may be a network element, such as an accesspoint (AP) in a WLAN, or may be a base station (BTS) in a GSM network, aGPRS network, or a CDMA network, or may be a base station (NodeB) in aCDMA 2000 network or a WCDMA network, or may be an evolved NodeB (eNB)in an LTE network, or may be an access service network base station (ASNBS) in a WiMAX network; or may be a network element, such as theforegoing access point, a controller of a base station, or anauthenticator.

FIG. 1 is a flowchart of Embodiment 1 of a method for accessing anetwork by a piece of user equipment according to the present invention.This embodiment is described by using an example in which a source sideaccess device is used as an execution body. As shown in FIG. 1, themethod of this embodiment may include the following content:

S101. A source side access device sends an access indication message toa UE, where the access indication message is used to instruct the UE toaccess a target side access device; or a source side access device sendsa first notification message to a target side access device, where thefirst notification message is used to instruct the target side accessdevice to send, to a UE, access information used to instruct the UE toaccess the target side access device.

S102. In a process in which the UE accesses the target side accessdevice, the source side access device maintains a connection between theUE and the source side access device.

The connection between the UE and the source side access device includesa control plane connection between the UE and the source side accessdevice or a user plane connection between the UE and the source sideaccess device.

As an implementable manner, before the sending, by a source side accessdevice, an access indication message to a UE, the method furtherincludes: receiving, by the source side access device, the accessindication message sent by a centralized control node.

Optionally, before the sending, by a source side access device, anaccess indication message to a UE, the method further includes:

-   -   determining, by the source side access device, that the user        equipment UE is in a coverage range of the target side access        device.

As an example, the source side access device currently is serving theUE, the source side access device first determines that the UE is in thecoverage range of the target side access device, and there are twoimplementable manners used by the source side access device to performthe determining. As an optional implementation manner, before the sourceside access device determines that the UE is in the coverage range ofthe target side access device, the source side access device receives afirst discovery message reported by the UE, where the first discoverymessage is used to indicate that the UE detects the target side accessdevice. As another optional implementation manner, before the sourceside access device determines that the UE is in the coverage range ofthe target side access device, the source side access device receives asecond discovery message reported by the target side access device,where the second discovery message is used to indicate that the targetside access device detects that the UE is in the coverage range of thetarget side access device. For example, a source side uplink receivermay be installed on the target side access device, where the source sideuplink receiver may be configured to receive an uplink signal sent bythe UE to the source side access device, and the target side accessdevice may determine, according to strength of the uplink signal,whether the UE is in the coverage range of the target side accessdevice. When the target side access device detects, by using the uplinkreceiver, that the UE is in the coverage range of the target side accessdevice, the target side access device reports the second discoverymessage report to the source side access device, and when receiving thesecond discovery message, the source side access device may determinethat the UE is in the coverage range of the target side access device.

In S101, as an optional implementation manner, the source side accessdevice sends the access indication message to the UE, where the accessindication message is used to instruct the UE to access the target sideaccess device.

Optionally, if the source side access device exchanges information withthe target side access device before the access indication message issent, the access indication message may include information about anaccess feature of the target side access device and information about aresource reserved by the target side access device for the UE, where theinformation about the access feature may include an identifier, such asa service set identifier (Service Set Identifier, SSID for short), acarrier of Wifi, or a WLAN standard, of a target side, so that afterreceiving the information about the access feature, the UE accesses acorresponding target side according to the identifier of the targetside; and the target side access device reserves a resource for the UE,so that after accessing the target side access device, the UE does notneed to wait for resource allocation.

Optionally, the access indication message is further used to: after theUE accesses the target side access device, instruct the UE to maintainthe connection between the UE and the source side access device, ordisconnect the connection between the UE and the source side accessdevice. For example, indication information is represented by using anindication bit, where when the indication bit is 1, the UE is instructedto maintain, after the UE accesses the target side access device, acurrent connection between the UE and the source side access device, andmaintain a bearer that is not transferred; or when the indication bit is0, the UE is instructed to release a current connection, that is,disconnect a current connection between the UE and the source sideaccess device, and release a resource, which can reduce load of thesource side access device.

As another optional implementation manner, the source side access devicesends a notification message to the target side access device, where thenotification message is used to instruct the target side access deviceto initiate a connection to the UE, so that the UE maintains theconnection between the UE and the source side access device and accessesthe target side access device. Before the source side access devicesends the notification message to the target side access device, thesource side access device sends an enabling message to the UE, where theenabling message is used to instruct the UE to enable a module forcommunicating with the target side access device.

After S101, that is, after the source side access device determines thatthe UE is in the coverage range of the target side access device, atleast one bearer is transferred, and there are two implementablemanners:

As an optional implementation manner, the source side access devicesends a first bearer transfer message to the UE, where the first bearertransfer message carries a bearer identifier of a bearer between the UEand the source side access device, and the bearer identifier is used toinstruct the UE to transfer a bearer corresponding to the beareridentifier to the target side access device; as another optionalimplementation manner, the source side access device sends a beareridentifier of a bearer between the UE and the source side access deviceto the target side access device, where the bearer identifier of thebearer between the UE and the source side access device is used toinstruct the target side access device to send a second bearer transfermessage to the UE, where the second bearer transfer message is used toinstruct the UE to transfer a bearer corresponding to the beareridentifier to the target side access device. At least one bearer isselectively transferred, which improves flexibility, and can providebetter performance according to different features of a source side anda target side. It should be noted herein that the bearer transfermessage for bearer transfer may be sent before or after the UEestablishes a connection to a target side; and if the bearer transfermessage is sent before the UE establishes a connection to the targetside, the bearer transfer message and the access indication message maybe jointly sent, where the bearer transfer message may be independent,or may be included in the access indication message.

Optionally, the access indication message is further used to: after theUE accesses the target side access device, instruct the UE to enter adiscontinuous reception (DRX for short below) mode, where when the UEenters the DRX mode, the UE only needs to perform waking up at a momentspecified by a DRX configuration, to listen to a wireless channel, andduring the rest of time, the UE may disable a receiver thereof, whichsaves more electricity for the UE.

According to the method, provided in this embodiment, for accessing anetwork by a piece of user equipment, a source side access device sendsan access indication message to a UE, where the access indicationmessage is used to instruct the UE to access a target side accessdevice, or a source side access device sends a first notificationmessage to a target side access device, where the first notificationmessage is used to instruct the target side access device to send, to aUE, access information used to instruct the UE to access the target sideaccess device; and in a process in which the UE accesses the target sideaccess device, the source side access device maintains a connectionbetween the UE and the source side access device. Therefore, in theprocess in which the UE accesses the target side access device, thesource side access device maintains the connection between the UE andthe source side access device; therefore, a service interruption is notcaused.

FIG. 2 is a flowchart of Embodiment 2 of a method for accessing anetwork by a piece of user equipment according to the present invention.This embodiment is described by using an example in which a UE is usedas an execution body. As shown in FIG. 2, the method of this embodimentmay include:

S201. A UE receives an access indication message sent by a source sideaccess device, where the access indication message is used to instructthe UE to access a target side access device; or a UE receives accessinformation that is sent by a target side access device and used toinstruct the UE to access the target side access device.

S202. The UE accesses the target side access device according to theaccess indication message or the access information.

In a process in which the UE accesses the target side access device, theUE maintains a connection between the UE and the source side accessdevice, where the connection between the UE and the source side accessdevice includes a control plane connection between the UE and the sourceside access device or a user plane connection between the UE and thesource side access device.

In S201, as an optional implementation manner, the UE receives theaccess indication message sent by the source side access device, wherethe access indication message is used to instruct the UE to access thetarget side access device. Before the UE receives the access indicationmessage sent by the source side access device, when detecting the targetside access device, the UE reports a first discovery message to thesource side access device, where the first discovery message is used toindicate that the UE detects the target side access device.

Optionally, if the source side access device exchanges information withthe target side access device before the access indication message issent, the access indication message may include information about anaccess feature of the target side access device and information about aresource reserved by the target side access device for the UE, where theinformation about the access feature may include an identifier of atarget side, so that after receiving the information about the accessfeature, the UE accesses a corresponding target side according to theidentifier of the target side; and the target side access devicereserves a resource for the UE, so that after accessing the target sideaccess device, the UE does not need to wait for resource allocation.

As another optional implementation manner, the UE receives a connectionestablishment request sent by the target side access device, wherebefore the UE receives the connection establishment request sent by thetarget side access device, the UE receives an enabling message sent bythe source side access device, where the enabling message is used toinstruct the UE to enable a module for communicating with the targetside access device, and the UE enables, according to the enablingmessage, the module for communicating with the target side accessdevice.

In S202, optionally, the access indication message is further used to:after the UE accesses the target side access device, instruct the UE tomaintain the connection between the UE and the source side accessdevice, or disconnect the connection between the UE and the source sideaccess device. For example, indication information is represented byusing an indication bit, where when the indication bit is 1, the UE isinstructed to maintain, after the UE accesses the target side accessdevice, a current connection between the UE and the source side accessdevice, and maintain a bearer that is not transferred; or when theindication bit is 0, the UE is instructed to release a currentconnection, that is, disconnect a current connection between the UE andthe source side access device, and release a resource, which can reduceload of the source side access device.

If the indication information is used to: after the UE accesses thetarget side access device, instruct to disconnect the connection betweenthe UE and the source side access device, after the UE accesses thetarget side access device, the method further includes:

S203. The UE disconnects the connection between the UE and the sourceside access device.

The accessing, by the UE, the target side access device according to theaccess indication message or the access information further includes:

As an optional implementation manner, the UE receives a first bearertransfer message sent by the source side access device, where the firstbearer transfer message carries a bearer identifier of a bearer betweenthe UE and the source side access device, and the bearer identifier isused to instruct the UE to transfer a bearer corresponding to the beareridentifier to the target side access device.

As another optional implementation manner, the UE receives a secondbearer transfer message sent by the target side access device, where thesecond bearer transfer message is used to instruct the UE to transfer abearer corresponding to a bearer identifier to the target side accessdevice.

As still another optional implementation manner, the UE sends a trafficflow template (TFT for short below), a procedure transaction identifier(PTI for short below), and an identifier of a bearer on a network side(an EPS bearer Identity) to the source side access device, where theTFT, the PTI, and the bearer identifier on the network side are used bythe source side access device to stop using a bearer that corresponds tothe bearer identifier between the UE and the source side access deviceto exchange data with the UE.

A bearer is selectively transferred, which improves flexibility, and canprovide better performance according to different features of a sourceside and a target side.

Optionally, the access indication message is further used to: after theUE accesses the target side access device, instruct the UE to enter aDRX mode, and the method further includes:

-   -   entering, by the UE, the DRX mode according to the access        indication message to exchange data with the source side access        device, or exchange data with the target side access device,        where when the UE enters the DRX mode, the UE only needs to        perform waking up at a moment specified by a DRX configuration,        to listen to a wireless channel, and during the rest of time,        the UE may disable a receiver thereof, which saves more        electricity for the UE.

According to the method, provided in this embodiment, for accessing anetwork by a piece of user equipment, a UE receive an access indicationmessage sent by a source side access device, where the access indicationmessage is used to instruct the UE to access a target side accessdevice, or a UE receives access information that is sent by a targetside access device and used to instruct the UE access the target sideaccess device; and then the UE accesses the target side access deviceaccording to the access indication message or the access information. Inaddition, in a process in which the UE accesses the target side accessdevice, the UE maintains a connection between the UE and the source sideaccess device. Therefore, in the process in which the UE accesses thetarget side access device, the UE maintains the connection between theUE and the source side access device; therefore, a service interruptionis not caused.

FIG. 3 is a flowchart of Embodiment 3 of a method for accessing anetwork by a piece of user equipment according to the present invention.As shown in FIG. 3, this embodiment is described by using an example inwhich a centralized control node is used as an execution body. Themethod of this embodiment may include:

S10. A centralized control node sends an access indication message to asource side access device, so that the source side access device sendsthe access indication message to the source side access device, wherethe access indication message is used to instruct the UE to access atarget side access device; or

-   -   a centralized control node sends a second notification message        to a target side access device, where the second notification        message is used to instruct the target side access device to        send, to a UE, access information used to instruct the UE to        access the target side access device.

Further, the access indication message includes: information used toindicate an access feature of the target side access device andinformation used to indicate a resource reserved by the target sideaccess device for the UE.

Optionally, the access indication message is further used to: after theUE accesses the target side access device, instruct the UE to maintain aconnection between the UE and the source side access device, ordisconnect a connection between the UE and the source side accessdevice.

In the foregoing embodiment, optionally, the access indication messageis further used to: after the UE accesses the target side access device,instruct the UE to enter a DRX mode.

According to the method, provided in this embodiment, for accessing anetwork by a piece of user equipment, a centralized control node sendsan access indication message to a source side access device, so that thesource side access device sends the access indication message to thesource side access device, where the access indication message is usedto instruct the UE to access a target side access device, or acentralized control node sends a second notification message to a targetside access device, where the second notification message is used toinstruct the target side access device to send, to a UE, accessinformation used to instruct the UE to access the target side accessdevice. Therefore, in a process in which the UE accesses the target sideaccess device, the source side access device maintains a connectionbetween the UE and the source side access device; therefore, a serviceinterruption is not caused.

FIG. 4 is a flowchart of Embodiment 4 of a method for accessing anetwork by a piece of user equipment according to the present invention.As shown in FIG. 4, this embodiment is described by using an example inwhich after determining that a UE is in a coverage range of a targetside access device, a source side access device instructs the UE toaccess the target side access device or instructs the target side accessdevice to initiate a connection to the UE. The method of this embodimentmay include:

S301. A source side access device sends an access indication message toa UE, where the access indication message is used to instruct the UE toaccess a target side access device; or a source side access device sendsa notification message to a target side access device, where thenotification message is used to instruct the target side access deviceto send, to a UE, access information used to instruct the UE to accessthe target side access device.

S302. In a process in which the UE accesses the target side accessdevice, the source side access device maintains a connection between theUE and the source side access device.

The connection between the UE and the source side access device includesa control plane connection between the UE and the source side accessdevice or a user plane connection between the UE and the source sideaccess device.

As an implementable manner, before the sending, by a source side accessdevice, an access indication message to a UE, the method furtherincludes: receiving, by the source side access device, the accessindication message sent by a centralized control node.

Optionally, before the sending, by a source side access device, anaccess indication message to a UE, the method further includes:

-   -   determining, by the source side access device, that the user        equipment UE is in a coverage range of the target side access        device.

In S301, as an optional implementation manner, the source side accessdevice sends the access indication message to the UE, where the accessindication message is used to instruct the UE to access the target sideaccess device.

Optionally, if the source side access device exchanges information withthe target side access device before the access indication message issent, the access indication message may include information about anaccess feature of the target side access device and information about aresource reserved by the target side access device for the UE, where theinformation about the access feature may include an identifier, such asan SSID, a carrier of Wifi, or a WLAN standard, of a target side, sothat after receiving the information about the access feature, the UEaccesses a corresponding target side according to the identifier of thetarget side; and the target side access device reserves a resource forthe UE, so that after accessing the target side access device, the UEdoes not need to wait for resource allocation.

Optionally, the access indication message is further used to: after theUE accesses the target side access device, instruct the UE to maintainthe connection between the UE and the source side access device, ordisconnect the connection between the UE and the source side accessdevice. For example, indication information is represented by using anindication bit, where when the indication bit is 1, the UE is instructedto maintain, after the UE accesses the target side access device, acurrent connection between the UE and the source side access device, andmaintain a bearer that is not transferred; or when the indication bit is0, the UE is instructed to release a current connection, that is,disconnect a current connection between the UE and the source sideaccess device, and release a resource, which can reduce load of thesource side access device.

As another optional implementation manner, the source side access devicesends a notification message to the target side access device, where thenotification message is used to instruct the target side access deviceto initiate a connection to the UE, so that the UE maintains theconnection between the UE and the source side access device and accessesthe target side access device. Before the source side access devicesends the notification message to the target side access device, thesource side access device sends an enabling message to the UE, where theenabling message is used to instruct the UE to enable a module forcommunicating with the target side access device.

S303. The UE receives the access indication message sent by the sourceside access device, where the access indication message is used toinstruct the UE to access the target side access device; or the UEreceives the access information that is sent by the target side accessdevice and used to instruct the UE to access the target side accessdevice.

In a process in which the UE accesses the target side access device, theUE maintains the connection between the UE and the source side accessdevice, where the connection between the UE and the source side accessdevice includes a control plane connection between the UE and the sourceside access device or a user plane connection between the UE and thesource side access device.

S304. The UE accesses the target side access device according to theaccess indication message or the access information.

Optionally, the access indication message may include indicationinformation, where the indication information is used to: after the UEaccesses the target side access device, instruct the UE to maintain theconnection between the UE and the source side access device ordisconnect the connection between the UE and the source side accessdevice. If the indication information is used to: after the UE accessesthe target side access device, instruct to disconnect the connectionbetween the UE and the source side access device, after the UE accessesthe target side access device, the connection between the UE and thesource side access device is disconnected.

After S304, the method further includes: transferring, by the UE, atleast one bearer between the UE and the source side access device to thetarget side access device.

There are three implementable manners for transferring at least onebearer.

As an optional implementation manner, the UE receives a first bearertransfer message sent by the source side access device, where the firstbearer transfer message carries a bearer identifier of a bearer betweenthe UE and the source side access device, and the bearer identifier isused to instruct the UE to transfer a bearer corresponding to the beareridentifier to the target side access device.

As another optional implementation manner, the UE receives a secondbearer transfer message sent by the target side access device, where thesecond bearer transfer message is used to instruct the UE to transfer abearer corresponding to a bearer identifier to the target side accessdevice.

As still another optional implementation manner, the UE sends a TFT, aPTI, and an identifier of a bearer on a network side to the source sideaccess device, where the TFT, the PTI, and the bearer identifier on thenetwork side are used by the source side access device to stop using abearer that corresponds to the bearer identifier between the UE and thesource side access device to exchange data with the UE, so that thesource side access device stops using the bearer between the UE and thesource side access device to send data to the UE.

At least one bearer is selectively transferred, which improvesflexibility, and can provide better performance according to differentfeatures of a source side and a target side.

Optionally, the indication message further includes information forinstructing the UE to enter a DRX mode. When the UE enters the DRX modeafter receiving the information, the UE only needs to perform waking upat a moment specified by a DRX configuration, to listen to a wirelesschannel, and during the rest of time, the UE may disable a receiverthereof, which saves more electricity for the UE.

According to the method, provided in this embodiment, for accessing anetwork by a piece of user equipment, a source side access device sendsan access indication message to a UE, where the access indicationmessage is used to instruct the UE to access a target side accessdevice, or a source side access device sends a first notificationmessage to a target side access device, where the first notificationmessage is used to instruct the target side access device to send, to aUE, access information used to instruct the UE to access the target sideaccess device; the UE receives the access indication message sent by thesource side access device, or the UE receives the access informationthat is sent by the target side access device and used to instruct theUE to access the target side access device; and then the UE accesses thetarget side access device according to the access indication message orthe access information. In addition, in a process in which the UEaccesses the target side access device, the UE maintains a connectionbetween the UE and the source side access device. Therefore, in theprocess of accessing the target side access device by the UE, the UEmaintains the connection between the UE and the source side accessdevice; therefore, a service interruption is not caused.

The technical solutions of the method embodiments shown above aredescribed in detail by using several specific embodiments below.

FIG. 5 is a signaling flowchart of Embodiment 1 of a method foraccessing a network by a piece of user equipment according to thepresent invention. In this embodiment, for example, a source side accessdevice may be an LTE network, and a target side access device may beWIFI. This embodiment is described by using an example in which afterdetermining that a UE is in a coverage range of the target side accessdevice, the source side access device instructs the UE to access thetarget side access device. As shown in FIG. 5, the method of thisembodiment includes:

S401. A UE detects a target side access device.

S402. The UE reports a first discovery message to a source side accessdevice.

Optionally, the target side access device may further be used to detectwhether the UE is in a coverage range of the target side access device.For example, a source side uplink receiver may be installed on thetarget side access device, and when the target side access devicedetects, by using the uplink receiver, that the UE is in the coveragerange of the target side access device, the target side access devicereports, to the source side access device, a second discovery messageindicating that the UE is discovered; and when receiving the seconddiscovery message, the source side access device can determine that theUE is in the coverage range of the target side access device. In thiscase, S401 is: A target side access device detects that a UE is in acoverage range of the target side access device; and S402 is: The UEreports a second discovery message to a source side access device.

S403. After receiving the first discovery message or the seconddiscovery message, the source side access device determines that the UEis in the coverage range of the target side access device.

S404. The source side access device sends an access indication messageto the UE.

If the source side access device exchanges information with the targetside access device before the access indication message is sent, theaccess indication message may include information about an accessfeature of the target side access device and information about aresource reserved by the target side access device for the UE, where theinformation about the access feature may include an identifier of atarget side, so that after receiving the information about the accessfeature, the UE accesses a corresponding target side according to theidentifier of the target side; and the target side access devicereserves a resource for the UE, so that after accessing the target sideaccess device, the UE does not need to wait for resource allocation.

S405. The UE maintains a connection between the UE and the source sideaccess device, and accesses the target side access device.

Optionally, the access indication message may include indicationinformation, where the indication information is used to: after the UEaccesses the target side access device, instruct the UE to maintain theconnection between the UE and the source side access device ordisconnect the connection between the UE and the source side accessdevice. If the indication information is used to: after the UE accessesthe target side access device, instruct to disconnect the connectionbetween the UE and the source side access device, in S405, after the UEaccesses the target side access device, the connection between the UEand the source side access device is disconnected.

S406. The UE transfers at least one bearer between the UE and the sourceside access device to the target side access device.

There are three implementable manners for transferring at least onebearer.

In a first manner, S406 includes the following steps:

S406 a. The source side access device sends a bearer transfer message tothe UE, where the bearer transfer message carries a bearer identifier.

S406 b. After receiving the bearer transfer message sent by the sourceside access device, the UE transfers a bearer corresponding to thebearer identifier to the target side access device.

In a second manner, S406 includes the following steps:

S406 c. The source side access device sends bearer information to thetarget side access device, where the bearer information carries a beareridentifier of a bearer between the UE and the source side access device.

S406 d. The target side access device sends a bearer transfer message tothe UE, where the bearer transfer message includes an identifier of abearer that needs to be transferred or an identifier of a bearer on anetwork side that needs to be transferred.

S406 e. After receiving the bearer transfer message sent by the targetside access device, the UE transfers a bearer corresponding to thebearer identifier to the target side access device. It should be notedherein that the bearer transfer message for bearer transfer may be sentbefore or after the UE establishes a connection to a target side; and ifthe bearer transfer message is sent before the UE establishes aconnection to the target side, the bearer transfer message and theaccess indication message may be jointly sent, where the bearer transfermessage may be independent, or may be included in the access indicationmessage.

In a third manner, S406 includes the following steps:

S406 f. The UE sends a TFT, a PTI, and an identifier of a bearer on anetwork side to the source side access device.

S406 g. The source side access device stops using at least one bearerbetween the UE and the source side access device to send data to the UE.

It should be noted herein that optionally, when the indication messagefurther includes information for instructing the UE to enter a DRX mode,the method may further include the following step:

-   -   after receiving the information for instructing the UE to enter        a DRX mode, entering, by the UE, the DRX mode.

FIG. 6 is a signaling flowchart of Embodiment 2 of a method foraccessing a network by a piece of user equipment according to thepresent invention. As shown in FIG. 6, a difference between thisembodiment and the embodiment shown in FIG. 5 lies only in: after stepS402, the method further includes:

S407. The source side access device forwards the received firstdiscovery message to a centralized control node.

Correspondingly, S403 is:

S403′. After receiving the first discovery message or the seconddiscovery message, the centralized control node determines that the UEis in the coverage range of the target side access device.

Correspondingly, S404 is:

S404′. The source side access device forwards, to the UE, an accessindication message sent by the centralized control node.

Before step S404′, the method further includes:

S408. The centralized control node sends the access indication messageto the source side access device, so that the source side access deviceforwards the access indication message to the UE after receiving theaccess indication message.

Other steps are the same, and are not described herein again.

FIG. 7 is a signaling flowchart of Embodiment 3 of a method foraccessing a network by a piece of user equipment according to thepresent invention. In this embodiment, for example, a source side accessdevice may be an LTE network, and a target side access device may beWIFI. A difference between this embodiment and the embodiments shown inFIG. 5 and FIG. 6 lies in that after determining that a UE is in acoverage range of the target side access device, the source side accessdevice does not send an access indication message to the UE, butinstructs the target side access device to initiate a connection to theUE. As shown in FIG. 7, step S501 to step S503 are the same as S401 toS403, respectively, in the embodiments shown in FIG. 5 and FIG. 6, andare not described herein again. After step S503, the method of thisembodiment includes:

S504. The source side access device sends an enabling message to the UE.

S505. After receiving the enabling message, the UE enables a module forcommunicating with the target side access device.

S506. The source side access device sends a notification message to thetarget side access device.

S507. After receiving the notification message, the target side accessdevice sends a connection establishment request to the UE, to establisha connection.

S508. The UE transfers at least one bearer between the UE and the sourceside access device to the target side access device.

There are three implementable manners for transferring at least onebearer.

In a first manner, S508 includes the following steps:

S508 a. The source side access device sends a bearer transfer message tothe UE, where the bearer transfer message carries a bearer identifier.

S508 b. After receiving the bearer transfer message sent by the sourceside access device, the UE transfers a bearer corresponding to thebearer identifier to the target side access device.

In a second manner, S508 includes the following steps:

S508 c. The source side access device sends bearer information to thetarget side access device, where the bearer information carries a beareridentifier of a bearer between the UE and the source side access device.

S508 d. The target side access device sends a bearer transfer message tothe UE, where the bearer transfer message includes an identifier of abearer that needs to be transferred or an identifier of a bearer on anetwork side that needs to be transferred.

S508 e. After the UE receives the bearer transfer message sent by thetarget side access device, steps in the following third manner areperformed to transfer a bearer corresponding to the bearer identifier tothe target side access device. It should be noted herein that the bearertransfer message for bearer transfer may be sent before or after the UEestablishes a connection to a target side; and if the bearer transfermessage is sent before the UE establishes a connection to the targetside, the bearer transfer message and the enabling message may bejointly sent, where the bearer transfer message may be independent, ormay be included in the enabling message.

In a third manner, S508 includes the following steps:

S508 f. The UE sends a TFT, a PTI, and an identifier of a bearer on anetwork side to the source side access device.

S508 g. The source side access device stops using at least one bearerbetween the UE and the source side access device to send data to the UE.

It should be noted herein that optionally, when the indication messagefurther includes information for instructing the UE to enter adiscontinuous reception DRX mode, the method may further include thefollowing step:

S509. After receiving the information for instructing the UE to enter aDRX mode, the UE enters the DRX mode.

Optionally, the method may further include the following step:

The source side access device sends indication information to the UE,where the indication information is used to: after the UE accesses thetarget side access device, instruct the UE to maintain a connectionbetween the UE and the source side access device or disconnect aconnection between the UE and the source side access device. If theindication information is used to: after the UE accesses the target sideaccess device, instruct to disconnect the connection between the UE andthe source side access device, after the UE accesses the target sideaccess device, the connection between the UE and the source side accessdevice is disconnected.

FIG. 8 is a signaling flowchart of Embodiment 4 of a method foraccessing a network by a piece of user equipment according to thepresent invention. As shown in FIG. 8, a difference between thisembodiment and the embodiment shown in FIG. 7 lies only in: after S502,the method further includes:

S510. The source side access device forwards the received firstdiscovery message to a centralized control node.

Correspondingly, S503 is:

S503′. After receiving the first discovery message or the seconddiscovery message, the centralized control node determines that the UEis in a coverage range of the target side access device.

Correspondingly, S504 is:

S504′. The source side access device forwards, to the UE, an enablingmessage sent by the centralized control node.

Before S504′, the method further includes:

S511. The centralized control node sends the enabling message to thesource side access device, so that the source side access deviceforwards the enabling message to the UE after receiving the enablingmessage.

S506 is changed into:

S506′. The centralized control node sends a notification message to thetarget side access device.

Other steps are the same, and are not described herein again.

Persons of ordinary skill in the art may understand that all or some ofthe steps of the foregoing method embodiments may be implemented by aprogram instructing relevant hardware. The aforementioned program may bestored in a computer readable storage medium. When the program isexecuted, steps including the steps of the foregoing method embodimentsare performed. The aforementioned storage medium includes: any mediumthat can store program code, such as a ROM, a RAM, a magnetic disk, oran optical disc.

FIG. 9 is a schematic structural diagram of Embodiment 1 of an accessdevice according to the present invention. As shown in FIG. 9, theaccess device of this embodiment may include a sending module 12 and aprocessing module 13, where

-   -   the sending module 12 is configured to send an access indication        message to a piece of user equipment UE, where the access        indication message is used to instruct the UE to access a target        side access device; or configured to send a first notification        message to a target side access device, where the first        notification message is used to instruct the target side access        device to send, to a UE, access information used to instruct the        UE to access the target side access device; and    -   the processing module 13 is configured to: in a process in which        the UE accesses the target side access device, maintain a        connection between the UE and the source side access device,        where    -   the connection between the UE and the source side access device        includes a control plane connection between the UE and the        source side access device or a user plane connection between the        UE and the source side access device.

The access device of this embodiment may be configured to perform thetechnical solution of the method embodiment shown in FIG. 1, and animplementation principle thereof is similar, which is not describedherein again.

According to the access device provided in this embodiment, a sendingmodule sends an access indication message to a UE or sends a firstnotification message to a target side access device; and in a process inwhich the UE accesses the target side access device, a processing modulemaintains a connection between the UE and a source side access device.Therefore, in the process in which the UE accesses the target sideaccess device, the UE maintains the connection between the UE and thesource side access device; therefore, a service interruption is notcaused.

FIG. 10 is a schematic structural diagram of Embodiment 2 of an accessdevice according to the present invention. Based on the access deviceshown in FIG. 9, as shown in FIG. 10, the access device of thisembodiment may further include: a receiving module 14, where thereceiving module 14 is configured to: before the sending module 12 sendsthe access indication message to the UE, receive the access indicationmessage sent by a centralized control node.

Further, the access indication message includes: information used toindicate an access feature of the target side access device andinformation used to indicate a resource reserved by the target sideaccess device for the UE.

Optionally, the access indication message is further used to: after theUE accesses the target side access device, instruct the UE to maintainthe connection between the UE and the source side access device, ordisconnect the connection between the UE and the source side accessdevice.

In the foregoing embodiment, the sending module 12 is further configuredto:

-   -   send a first bearer transfer message to the UE, where the first        bearer transfer message carries a bearer identifier of a bearer        between the UE and the source side access device, and the bearer        identifier is used to instruct the UE to transfer a bearer        corresponding to the bearer identifier to the target side access        device.

In the foregoing embodiment, the sending module 12 is further configuredto:

-   -   send a bearer identifier of a bearer between the UE and the        source side access device to the target side access device,        where the bearer identifier of the bearer between the UE and the        source side access device is used to instruct the target side        access device to send a second bearer transfer message to the        UE, where the second bearer transfer message is used to instruct        the UE to transfer a bearer corresponding to the bearer        identifier to the target side access device.

In the foregoing embodiment, the access indication message is furtherused to: after the UE accesses the target side access device, instructthe UE to enter a discontinuous reception DRX mode.

The access device of this embodiment may be configured to perform thetechnical solution of the method embodiment shown in FIG. 1, and animplementation principle thereof is similar, which is not describedherein again.

According to the access device provided in this embodiment, a receivingmodule receives an access indication message sent by a centralizedcontrol node; a sending module sends an access indication message to aUE or sends a first notification message to a target side access device;and in a process in which the UE accesses the target side access device,a processing module maintains a connection between the UE and a sourceside access device. Therefore, in the process in which the UE accessesthe target side access device, the UE maintains the connection betweenthe UE and the source side access device; therefore, a serviceinterruption is not caused.

FIG. 11 is a schematic structural diagram of Embodiment 3 of an accessdevice according to the present invention. As shown in FIG. 11, theaccess device of this embodiment may include a receiving module 21 and aprocessing module 22, where

-   -   the receiving module 21 is configured to receive an access        indication message sent by a source side access device, where        the access indication message is used to instruct a UE to access        a target side access device; or configured to receive access        information that is sent by a target side access device and used        to instruct a UE to access the target side access device; and    -   the processing module 22 is configured to access the target side        access device according to the access indication message or the        access information, where    -   in a process in which the UE accesses the target side access        device, the UE maintains a connection between the UE and the        source side access device, where the connection between the UE        and the source side access device includes a control plane        connection between the UE and the source side access device or a        user plane connection between the UE and the source side access        device.

The access device of this embodiment may be configured to perform thetechnical solution of the method embodiment shown in FIG. 2, and animplementation principle thereof is similar, which is not describedherein again.

According to the access device provided in this embodiment, a receivingmodule receives an access indication message sent by a source sideaccess device or receives access information that is sent by a targetside access device and used to instruct a UE to access the target sideaccess device; and a processing module accesses the target side accessdevice according to the access indication message or the accessinformation. Therefore, in a process in which the UE accesses the targetside access device, the UE maintains a connection between the UE and thesource side access device; therefore, a service interruption is notcaused.

FIG. 12 is a schematic structural diagram of Embodiment 4 of an accessdevice according to the present invention. As shown in FIG. 12, based onthe structure of the access device shown in FIG. 11, the access deviceof this embodiment further includes a sending module 24, where

-   -   the sending module 24 is configured to report a first discovery        message to the source side access device, where the first        discovery message is used to indicate the target side access        device detected by the UE; and    -   the processing module 22 is further configured to detect the        target side access device before the receiving module 21        receives the access indication message sent by the source side        access device.

In the foregoing embodiment, optionally, the access indication messageincludes: information used to indicate an access feature of the targetside access device and information used to indicate a resource reservedby the target side access device for the UE.

In the foregoing embodiment, optionally, the access indication messageis further used to: after the UE accesses the target side access device,instruct the UE to maintain the connection between the UE and the sourceside access device, or disconnect the connection between the UE and thesource side access device.

Further, if indication information is used to: after the UE accesses thetarget side access device, instruct to disconnect the connection betweenthe UE and the source side access device, the processing module 22 isfurther configured to: after the access module accesses the target sideaccess device, disconnect the connection between the UE and the sourceside access device.

In the foregoing embodiment, optionally, the receiving module 21 isfurther configured to:

-   -   receive a first bearer transfer message sent by the source side        access device, where the first bearer transfer message carries a        bearer identifier of a bearer between the UE and the source side        access device, and the bearer identifier is used to instruct the        UE to transfer a bearer corresponding to the bearer identifier        to the target side access device; or configured to receive a        second bearer transfer message sent by the target side access        device, where the second bearer transfer message is used to        instruct the UE to transfer a bearer corresponding to a bearer        identifier to the target side access device.

In the foregoing embodiment, the sending module 24 is further configuredto:

-   -   send a TFT, a PTI, and a bearer identifier of a bearer between        the UE and the source side access device to the source side        access device, where the TFT, the PTI, and the bearer identifier        of the bearer between the UE and the source side access device        are used by the source side access device to stop using a bearer        that corresponds to the bearer identifier of the bearer between        the UE and the source side access device to exchange data with        the UE.

In the foregoing embodiment, the access indication message is furtherused to: after the UE accesses the target side access device, instructthe UE to enter a DRX mode, and the processing module 22 is furtherconfigured to:

-   -   enter the DRX mode according to the access indication message to        exchange data with the source side access device, or exchange        data with the target side access device.

The access device of this embodiment may be configured to perform thetechnical solution of the method embodiment shown in FIG. 2, and animplementation principle thereof is similar, which is not describedherein again.

In Embodiment 1 of a centralized control node in the present invention,an access device of this embodiment may include: a sending module 30,where the sending module 30 is configured to send an access indicationmessage to a source side access device, so that the source side accessdevice sends the access indication message to the source side accessdevice, where the access indication message is used to instruct the UEto access a target side access device; or

-   -   configured to send a second notification message to a target        side access device, where the second notification message is        used to instruct the target side access device to send, to a UE,        access information used to instruct the UE to access the target        side access device.

Further, the access indication message includes: information used toindicate an access feature of the target side access device andinformation used to indicate a resource reserved by the target sideaccess device for the UE.

Further, the access indication message is further used to: after the UEaccesses the target side access device, instruct the UE to maintain aconnection between the UE and the source side access device, ordisconnect a connection between the UE and the source side accessdevice.

In the foregoing embodiment, the access indication message is furtherused to: after the UE accesses the target side access device, instructthe UE to enter a DRX mode.

According to the centralized control node provided in this embodiment, asending module sends an access indication message to a source sideaccess device, so that the source side access device sends the accessindication message to the source side access device, where the accessindication message is used to instruct the UE to access a target sideaccess device, or the centralized control node sends a secondnotification message to a target side access device, where the secondnotification message is used to instruct the target side access deviceto send, to a UE, access information used to instruct the UE to accessthe target side access device. Therefore, in a process in which the UEaccesses the target side access device, the source side access devicemaintains a connection between the UE and the source side access device;therefore, a service interruption is not caused.

FIG. 13 is a schematic structural diagram of Embodiment 5 of an accessdevice according to the present invention. As shown in FIG. 13, theaccess device of this embodiment may include a transmitter 31 and aprocessor 32, where

-   -   the transmitter 31 is configured to send an access indication        message to a piece of user equipment UE, where the access        indication message is used to instruct the UE to access a target        side access device; or configured to send a first notification        message to a target side access device, where the first        notification message is used to instruct the target side access        device to send, to a UE, access information used to instruct the        UE to access the target side access device; and    -   the processor 32 is configured to: in a process in which the UE        accesses the target side access device, maintain a connection        between the UE and the source side access device, where    -   the connection between the UE and the source side access device        includes a control plane connection between the UE and the        source side access device or a user plane connection between the        UE and the source side access device.

The access device of this embodiment may be configured to perform thetechnical solution of the method embodiment shown in FIG. 1, and animplementation principle thereof is similar, which is not describedherein again.

According to the access device provided in this embodiment, atransmitter sends an access indication message to a UE or sends a firstnotification message to a target side access device; and in a process inwhich the UE accesses the target side access device, a processormaintains a connection between the UE and a source side access device.Therefore, in the process in which the UE accesses the target sideaccess device, the UE maintains the connection between the UE and thesource side access device; therefore, a service interruption is notcaused.

FIG. 14 is a schematic structural diagram of Embodiment 6 of an accessdevice according to the present invention. Based on the access deviceshown in FIG. 13, as shown in FIG. 14, the access device of thisembodiment may further include: a receiver 33, where the receiver 33 isconfigured to: before the sending module sends the access indicationmessage to the UE, receive the access indication message sent by acentralized control node.

Further, the access indication message includes: information used toindicate an access feature of the target side access device andinformation used to indicate a resource reserved by the target sideaccess device for the UE.

Optionally, the access indication message is further used to: after theUE accesses the target side access device, instruct the UE to maintainthe connection between the UE and the source side access device, ordisconnect the connection between the UE and the source side accessdevice.

In the foregoing embodiment, the transmitter 31 is further configuredto:

-   -   send a first bearer transfer message to the UE, where the first        bearer transfer message carries a bearer identifier of a bearer        between the UE and the source side access device, and the bearer        identifier is used to instruct the UE to transfer a bearer        corresponding to the bearer identifier to the target side access        device.

In the foregoing embodiment, the transmitter 31 is further configuredto:

-   -   send a bearer identifier of a bearer between the UE and the        source side access device to the target side access device,        where the bearer identifier of the bearer between the UE and the        source side access device is used to instruct the target side        access device to send a second bearer transfer message to the        UE, where the second bearer transfer message is used to instruct        the UE to transfer a bearer corresponding to the bearer        identifier to the target side access device.

In the foregoing embodiment, the access indication message is furtherused to: after the UE accesses the target side access device, instructthe UE to enter a DRX mode.

The access device of this embodiment may be configured to perform thetechnical solution of the method embodiment shown in FIG. 1, and animplementation principle thereof is similar, which is not describedherein again.

FIG. 15 is a schematic structural diagram of Embodiment 7 of an accessdevice according to the present invention. As shown in FIG. 15, theaccess device of this embodiment may include a receiver 41 and aprocessor 42, where

-   -   the receiver 41 is configured to receive an access indication        message sent by a source side access device, where the access        indication message is used to instruct a UE to access a target        side access device; or configured to receive access information        that is sent by a target side access device and used to instruct        a UE to access the target side access device; and    -   the processor 42 is configured to access the target side access        device according to the access indication message or the access        information, where    -   in a process in which the UE accesses the target side access        device, the UE maintains a connection between the UE and the        source side access device, where the connection between the UE        and the source side access device includes a control plane        connection between the UE and the source side access device or a        user plane connection between the UE and the source side access        device.

The access device of this embodiment may be configured to perform thetechnical solution of the method embodiment shown in FIG. 2, and animplementation principle thereof is similar, which is not describedherein again.

According to the access device provided in this embodiment, a receiverreceives an access indication message sent by a source side accessdevice or receives access information that is sent by a target sideaccess device and used to instruct a UE to access the target side accessdevice; and a processor accesses the target side access device accordingto the access indication message or the access information. Therefore,in a process in which the UE accesses the target side access device, theUE maintains a connection between the UE and the source side accessdevice; therefore, a service interruption is not caused.

FIG. 16 is a schematic structural diagram of Embodiment 8 of an accessdevice according to the present invention. As shown in FIG. 16, based onthe structure of the access device shown in FIG. 15, the access deviceof this embodiment further includes a transmitter 43, where

-   -   the transmitter 43 is configured to report a first discovery        message to the source side access device, where the first        discovery message is used to indicate the target side access        device detected by the UE; and    -   the processor 42 is further configured to detect the target side        access device before the receiver 41 receives the access        indication message sent by the source side access device.

In the foregoing embodiment, optionally, the access indication messageincludes: information used to indicate an access feature of the targetside access device and information used to indicate a resource reservedby the target side access device for the UE.

In the foregoing embodiment, optionally, the access indication messageis further used to: after the UE accesses the target side access device,instruct the UE to maintain the connection between the UE and the sourceside access device, or disconnect the connection between the UE and thesource side access device.

Further, if indication information is used to: after the UE accesses thetarget side access device, instruct to disconnect the connection betweenthe UE and the source side access device, the processor 42 is furtherconfigured to: after the access module accesses the target side accessdevice, disconnect the connection between the UE and the source sideaccess device.

In the foregoing embodiment, optionally, the receiver 41 is furtherconfigured to:

-   -   receive a first bearer transfer message sent by the source side        access device, where the first bearer transfer message carries a        bearer identifier of a bearer between the UE and the source side        access device, and the bearer identifier is used to instruct the        UE to transfer a bearer corresponding to the bearer identifier        to the target side access device; or configured to receive a        second bearer transfer message sent by the target side access        device, where the second bearer transfer message is used to        instruct the UE to transfer a bearer corresponding to a bearer        identifier to the target side access device.

In the foregoing embodiment, the transmitter 43 is further configuredto:

-   -   send a TFT, a PTI, and a bearer identifier of a bearer between        the UE and the source side access device to the source side        access device, where the TFT, the PTI, and the bearer identifier        of the bearer between the UE and the source side access device        are used by the source side access device to stop using a bearer        that corresponds to the bearer identifier of the bearer between        the UE and the source side access device to exchange data with        the UE.

In the foregoing embodiment, the access indication message is furtherused to: after the UE accesses the target side access device, instructthe UE to enter a DRX mode, and the processor 42 is further configuredto:

-   -   enter the DRX mode according to the access indication message to        exchange data with the source side access device, or exchange        data with the target side access device.

The access device of this embodiment may be configured to perform thetechnical solution of the method embodiment shown in FIG. 2, and animplementation principle thereof is similar, which is not describedherein again.

In Embodiment 2 of a centralized control node in the present invention,an access device of this embodiment may include: a transmitter, wherethe transmitter is configured to send an access indication message to asource side access device, so that the source side access device sendsthe access indication message to the source side access device, wherethe access indication message is used to instruct the UE to access atarget side access device; or

-   -   configured to send a second notification message to a target        side access device, where the second notification message is        used to instruct the target side access device to send, to a UE,        access information used to instruct the UE to access the target        side access device.

Further, the access indication message includes: information used toindicate an access feature of the target side access device andinformation used to indicate a resource reserved by the target sideaccess device for the UE.

Further, the access indication message is further used to: after the UEaccesses the target side access device, instruct the UE to maintain aconnection between the UE and the source side access device, ordisconnect a connection between the UE and the source side accessdevice.

In the foregoing embodiment, the access indication message is furtherused to: after the UE accesses the target side access device, instructthe UE to enter a DRX mode.

According to the centralized control node provided in this embodiment, atransmitter sends an access indication message to a source side accessdevice, so that the source side access device sends the accessindication message to the source side access device, where the accessindication message is used to instruct the UE to access a target sideaccess device, or the centralized control node sends a secondnotification message to a target side access device, where the secondnotification message is used to instruct the target side access deviceto send, to a UE, access information used to instruct the UE to accessthe target side access device. Therefore, in a process in which the UEaccesses the target side access device, the source side access devicemaintains a connection between the UE and the source side access device;therefore, a service interruption is not caused.

Finally, it should be noted that the foregoing embodiments are merelyintended for describing the technical solutions of the presentinvention, but not for limiting the present invention. Although thepresent invention is described in detail with reference to theaforementioned embodiments, persons of ordinary skill in the art shouldunderstand that they may still make modifications to the technicalsolutions described in the aforementioned embodiments or make equivalentreplacements to some or all technical features thereof, withoutdeparting from the scope of the technical solutions of the embodimentsof the present invention.

What is claimed:
 1. An apparatus comprising: one or more processorscoupled with memory storing instructions which, when executed by the oneor more processors, cause the apparatus to: receive from a source accessdevice, an access indication message instructing the apparatus to accessa target access device; access the target access device according to theaccess indication message; receive from the source access device, abearer transfer message, wherein the bear transfer message carries anidentifier of a bearer between the apparatus and the source accessdevice; and transfer the bearer from the source access device to thetarget access device; wherein a connection between the apparatus and thesource access device is maintained, and the connection comprises acontrol plane connection between the apparatus and the source accessdevice or a user plane connection between the apparatus and the sourceaccess device.
 2. The apparatus according to claim 1, wherein the bearertransfer message and the access indication message are in a samemessage.
 3. The apparatus according to claim 1, wherein the instructionsfurther case the apparatus to: detect the target access device; andreport to the source access device, the target access device beingdetected.
 4. The apparatus according to claim 1, wherein the accessindication message includes an identifier of the target access device,and information about a resource reserved by the target access devicefor the apparatus.
 5. The apparatus according to claim 1, wherein theaccess indication message includes information for instructing theapparatus to enter a discontinuous reception (DRX) mode.
 6. Theapparatus according to claim 1, wherein the access indication messagefurther instructs the apparatus to maintain the connection between theapparatus and the source access device.
 7. The apparatus according toclaim 1, wherein the apparatus is a terminal device.
 8. A methodcomprising: receiving, by a terminal device from a source access device,an access indication message instructing the terminal device to access atarget access device; accessing, by the terminal device, the targetaccess device according to the access indication message; receiving, bythe terminal device from the source access device, a bearer transfermessage, wherein the bear transfer message carries an identifier of abearer between the terminal device and the source access device; andtransferring, by the terminal device, the bearer from the source accessdevice to the target access device; wherein a connection between theterminal device and the source access device is maintained, and theconnection comprises a control plane connection between the terminaldevice and the source access device or a user plane connection betweenthe terminal device and the source access device.
 9. The methodaccording to claim 8, wherein the bearer transfer message and the accessindication message are in a same message.
 10. The method according toclaim 8, further comprising: detecting, by the terminal device, thetarget access device; and reporting, by the terminal device to thesource access device, the target access device being detected.
 11. Themethod according to claim 8, wherein the access indication messageincludes an identifier of the target access device, and informationabout a resource reserved by the target access device for the terminaldevice.
 12. The method according to claim 8, wherein the accessindication message includes information for instructing the terminaldevice to enter a DRX mode.
 13. The method according to claim 8, whereinthe access indication message further instructs the terminal device tomaintain the connection between the terminal device and the sourceaccess device.
 14. An apparatus comprising: one or more processorscoupled with memory storing instructions which, when executed by the oneor more processors, cause the apparatus to: send, to a terminal device,an access indication message instructing the terminal device to access atarget access device; send, to the terminal device, a bearer transfermessage, wherein the bear transfer message carries an identifier of abearer between the terminal device and a source access device; maintaina connection with the terminal device; wherein the connection comprisesa control plane connection between the apparatus and the terminal deviceor a user plane connection between the apparatus and terminal device.15. The apparatus according to claim 14, wherein the bearer transfermessage and the access indication message are in a same message.
 16. Theapparatus according to claim 14, wherein the instructions further casethe apparatus to: exchange information with the target access device,wherein the information includes an identifier of the target accessdevice, and information about a resource reserved by the target accessdevice for the terminal device.
 17. The apparatus according to claim 14,wherein the access indication message includes the identifier of thetarget access device, and information about a resource reserved by thetarget access device for the terminal device.
 18. The apparatusaccording to claim 14, wherein the access indication message includesinformation for instructing the apparatus to enter a DRX mode.
 19. Theapparatus according to claim 14, wherein the access indication messagefurther instructs the terminal device to maintain the connection betweenthe apparatus and the terminal device.
 20. A telecommunication systemcomprising: a source access device; and, a target access device,wherein: the target access device is configured to exchange informationwith the source access device, wherein the information includes anidentifier of the target access device, and information about a resourcereserved by the target access device for a terminal device; the sourceaccess device is configured to send an access indication messageinstructing the terminal device to access the target access device, andthe access indication message includes the identifier of the targetaccess device, and the information about the resource reserved by thetarget access device for the terminal device.